The present invention relates to a pneumatic radial tire, and more particularly to a tread pattern for pneumatic radial tires for trucks or buses, in which stone entrapment in the zigzag, grooves of the tread is prevented without loss of the wet grip property of the tire.
In a pneumatic raidal tire particularly one for heavy load use such as a radial tire for trucks or buses, stone entrapment in the tread grooves is liable to occur under dirt road running. If the tire runs continuously under such a condition, stones are entrapped in the tread grooves, which inflict cracks and other injuries to the tread grooves.
As countermeasures for such problems, there have been attempts to widen the tread grooves and to provide stepped sidewalls for the tread grooves in order to make it easy to discharge the trapped stones from the tread grooves and to prevent the groove bottom from being reached by the stones.
Such attempts, however, have disadvantages in that the wear resistance is lowered and the width of the tread grooves decreases as the tread wears out which reduces the wet grip property.